Thermography is an image-forming process including a heating step and hence includes photothermography in which the image-forming process includes image-wise exposure and direct thermal processes in which the image-forming process includes an image-wise heating step. In direct thermal printing a visible image pattern is produced by image-wise heating of a recording material.
EP-A 0 752 616 discloses a thermographic material comprising at least one element and wherein said element(s) contain(s) therein a substantially light-insensitive organic heavy metal salt and an organic reductor therefor, the said material being capable of thermally producing an image from said organic heavy metal salt and reductor, wherein said material contains a 1,3-benzoxazine-2,4-dione toning agent having general formula (I):
wherein R1 represents hydrogen, —CH2OH, —(C═O)—R, —CONHR, or M; R2, R3, R4 and R5 each independently represents hydrogen, —O—(C═O)—OR or —NH—(C═O)—OR and at least one of which is not hydrogen if R1 is also hydrogen; R represents an alkyl or aryl group either of which may be substituted; and M represents a monovalent heavy metal ion. EP-A 0 752 616 further discloses that the film-forming binder of the recording layer containing the substantially light-insensitive organic heavy metal salt may be all kinds of natural, modified natural or synthetic resins or mixtures of such resins, wherein the organic heavy metal salt can be dispersed homogeneously: e.g. cellulose derivatives such as ethylcellulose, cellulose esters, e.g. cellulose nitrate, carboxymethylcellulose, starch ethers, galactomannan, polymers derived from α,β-ethylenically unsaturated compounds such as polyvinyl chloride, after-chlorinated polyvinyl chloride, copolymers of vinyl chloride and vinylidene chloride, copolymers of vinyl chloride and vinyl acetate, polyvinyl acetate and partially hydrolyzed polyvinyl acetate, polyvinyl alcohol, polyvinyl acetals that are made from polyvinyl alcohol as starting material in which only a part of the repeating vinyl alcohol units may have reacted with an aldehyde, preferably polyvinyl butyral, copolymers of acrylonitrile and acrylamide, polyacrylic acid esters, polymethacrylic acid esters, polystyrene and polyethylene or mixtures thereof. EP-A 0 752 616 also alludes to binders suitable for use in the non-organic silver salt containing donor layers used in reductor transfer printing which include: cellulose derivatives, such as ethyl cellulose, methyl cellulose, cellulose nitrate, cellulose acetate formate, cellulose acetate hydrogen phthalate, cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate pentanoate, cellulose acetate benzoate, cellulose triacetate; vinyl-type resins and derivatives, such as polyvinyl acetate, polyvinyl butyral, copolyvinyl butyral-vinyl acetal-vinyl alcohol, polyvinyl pyrrolidone, polyvinyl acetoacetal, polyacrylamide; polymers and copolymers derivated from acrylates and acrylate derivatives, such as polymethyl methacrylate and styrene-acrylate copolymers; polyester resins; polycarbonates; copoly(styrene-co-acrylonitrile); polysulfones; polyphenylene oxide; organosilicones, such as polysiloxanes; epoxy resins and natural resins, such as gum arabic. Preferably, the binder for the donor layer of the present invention comprises poly(styrene-co-acrylonitrile) or a mixture of poly(styrene-co-acrylonitrile) and a toluenesulphonamide condensation product.
EP-A 0 809 144 discloses a substantially non-photosensitive recording material comprising a thermosensitive element comprising a substantially light-insensitive organic silver salt, an organic reducing agent therefor in thermal working relationship therewith and a binder, on a support, characterized in that said thermosensitive element further comprises in reactive association with said substantially light-insensitive organic silver salt and said organic reducing agent a substituted or unsubstituted 1,2,4-triazole compound with at least one of the nitrogen atoms having a hydrogen atom and none of the carbon atoms being part of a thione-group, said compound not being annulated with an aromatic ring system. EP-A 0 809 144 further discloses that suitable binders for the thermosensitive element may be all kinds of natural, modified natural or synthetic resins or mixtures of such resins, wherein the organic heavy metal salt can be dispersed homogeneously: e.g. cellulose derivatives such as ethylcellulose, cellulose esters, e.g. cellulose nitrate, carboxymethylcellulose, starch ethers, galactomannan, polymers derived from α,β-ethylenically unsaturated compounds such as polyvinyl chloride, after-chlorinated polyvinyl chloride, copolymers of vinyl chloride and vinylidene chloride, copolymers of vinyl chloride and vinyl acetate, polyvinyl acetate and partially hydrolyzed polyvinyl acetate, polyvinyl alcohol, polyvinyl acetals that are made from polyvinyl alcohol as starting material in which only a part of the repeating vinyl alcohol units may have reacted with an aldehyde, preferably polyvinyl butyral, copolymers of acrylonitrile and acrylamide, polyacrylic acid esters, polymethacrylic acid esters, polystyrene and polyethylene or mixtures thereof.
JP 2001-13618A discloses a heat developing sensitive material containing organic silver, a photosensitive silver halide, a developer, and a binder resin at least on a base material, said binder resin containing a polyvinyl aceto acetal resin in 70% by weight or more among [all] the binder resin, said polyvinyl aceto acetal resin being characterized by the degree of acetalization of more than 50 mol %. Furthermore, JP 2001-13618A discloses the following resins: polyvinyl aceto acetals from Sekisui Chemical types KS-10, KS-1 and KS-5Z; an aceto acetal/hydroxyl-group/acetyl group=88.3 mol/10.2 mol/1.5 mol resin; an aceto acetal/butyral/hydroxyl-group/acetyl group=68.5 mol/22.8 mol/8.3 mol/0.4 mol resin; a polyvinyl alcohol acetalized by acetaldehyde and butyraldehyde from DENKI KAGAKU KOGYO K.K. type DENKA butyral #3000K; and Butvar B-79 from SOLUTIA; and that the polyvinyl aceto acetal resin can also be used for an under-coating layer or a back-coat layer.
EP-A 1 241 520 discloses a silver salt photothermographic dry imaging material comprising a support having thereon a photosensitive layer comprising silver aliphatic carboxylate grains and photosensitive silver halide grains, a reducing agent for silver ions, a binder and a cross-linking agent, wherein the photothermographic material has a silver coverage of 1.0 to 1.7 g/m2; the photosensitive silver halide grains have a mean grain size of 0.03 to 0.05 μm and a degree of grain size dispersity of not more than 30%; after the dry imaging material has been subjected to photothermographic processing at a temperature of 100 to 200° C. for 5 to 50 seconds, the photosensitive layer exhibits a thermal transition temperature of 46 to 200° C. In the silver salt photothermographic dry imaging material of the invention, as binder incorporated in the photosensitive layer, which includes such as silver aliphatic carboxylates, photosensitive silver halide grains and reducing agent on a support, can be employed high polymers well known in the art. The high polymers have a Tg of 70 to 105° C. The examples include: compounds comprised of polymers or copolymers containing ethylenically unsaturated monomers as constitutive units such as vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, acrylic acid, acrylate ester, vinylidene chloride, acrylonitrile, methacrylic acid, methacrylate ester, styrene, butadiene, ethylene, vinyl butyral, vinyl aceto-acetal and vinyl ether; polyurethane resins and various kinds of rubber resin. Constitutions of high polymers according to the invention of EP-A 1 241 520 are given in Table 1 and include the following polymers with butyral and aceto-acetal groups:
TABLE 1hydroxylTgPolymerAceto-acetalButyralacetalacetylgroupvaluename[mol %][mol %][mol %][mol %][mol %][° C.]P-16473.71.724.685P-23775.01.623.475P-57371.11.627.388P-83774.40.624.075P-93775.41.624.074The use of Polymers P-2 and P-5 in the photosensitive layer of the silver salt photothermographic dry imaging material is exemplified.
EP-A 1 270 608, which corresponds to WO 01/053357A1 and JP 2002-201215, discloses a polyvinyl acetal resin for heat-developable photosensitive materials which is a polyvinyl acetal resin synthesized by the acetalization reaction between a polyvinyl alcohol and an aldehyde and which comprises having a degree of polymerization of 200 to 3,000, a residual acetyl group content of 0 to 25 mole percent and a residual hydroxyl content of 17 to 35 mole percent, as calculated while regarding one acetal group as two acetalized hydroxyl groups, a water content of not more than 2.5% by weight and a residual aldehyde content of not more than 10 ppm and is free of any antioxidant, perferably having a glass transition temperature of 55 to 110° C. Resins containing vinyl alcohol, vinyl acetal and vinyl butyral monomer units are disclosed in Examples 4, 5, 6 and 8 with glass transition temperatures of 80, 70, 76, 103 and 93° C. respectively of EP-1 270 608 and had the compositions given in Table 2:
TABLE 2vinylacetal{mol %/vinyl butyralvinyl alcoholvinyl acetatewt %][mol %/wt %][mol %/wt %][mol %/wt %]Example No.438/42.6  31/43.329.5/12.81.5/1.3535/37.8  33/44.4 21/8.8 11/9.0635/39.8  32/45.3  32/14.0  1/0.9773/86.2  1/1.5  25/11.4  1/0.9863/77.0  1/1.5  22/10.4  12/11.1ComparativeExample No.631/37.229.5/44.1  38/17.61.0/1.1
EP-1 278 101 discloses a photothermographic imaging material comprising a support having thereon a photosensitive layer comprising a photosensitive silver halide, a light-insensitive organic silver salt, a binder, and a reducing agent for silver ions, wherein the reducing agent is represented by the following Formula (S):
wherein Z is a group of atoms necessary to form a non aromatic ring of 3 to 10 members; Rx is a hydrogen or an alkyl group; each Ro′ and Ro″ is independently a hydrogen, an alkyl group, or a heterocyclic group; Qo is a substituent; and each n and m is independently an integer of 0 to 2; and plural Qo's may be the same or different. EP-A 1 278 101 further discloses the following polymers preferably employed in the invention:
TABLE 3hydroxylTgPolymerAceto-acetalButyralacetalacetylgroupvaluename[mol %][mol %][mol %][mol %][mol %][° C.]P-16473.71.724.685P-23775.01.623.475P-47371.11.627.388P-73774.41.624.075P-83775.41.623.074
EP-A 1 143 292 discloses a photothermographic material comprising a support having on one side of the support at least an image forming layer containing organic silver salt grains, light sensitive silver halide grains and a reducing agent and a surface protective layer, wherein the element composition on the surface of the image forming layer exhibits a ratio of the number of carbon elements to the number of oxygen elements of not more than 9, and wherein the element composition is obtained by X-ray photoelectron spectroscopy. Exemplary examples of binders disclosed for use in the image forming layer include polyvinyl acetals (e.g. polyvinyl formal, polyvinyl butyral). Of these binders vinyl acetals such as polyvinyl butyral and polyvinyl acetal, and cellulose esters such as cellulose acetate and cellulose acetate-butyrate are preferred, which may be used alone or in combination. Further, mixed acetals obtained from two aldehydes, such as polyvinyl acetobutyral are also preferred according to EP-A 1 143 292. However, such mixed acetals are not exemplified therein.
EP-A 1 136 877 discloses a photothermographic material comprising on a support light sensitive silver halide grains, an organic silver salt, a reducing agent and a binder, wherein the photothermographic material comprises a silane compound represented by formula (1) or (2):(R1O)m—Si-[(L1)xR2]n  formula (1)
wherein R1, R2, R3, R4, R5, R6, R7 and R8 represent each an alkyl group, an alkenyl group, an alkynyl group, an aryl group or a heterocyclic group; L1, L2, L3 and L4 represent each a bivalent linkage group; m and n are each an integer of t to 3, provided that m+n is 4; p1 and p2 are each an integer of 1 to 3 and q1 and q2 are each 0, 1 or 2, provided that p1+q1 and p2+q2 are each 3; r1 and t are each 0 or an integer of 1 to 1000; and x is 0 or 1. Binders usable on the organic solvent-based coating include cellulose derivatives, polyvinyl alcohol derivatives, acrylate polymer derivatives, polyimide derivatives, polyamide derivatives, phenol resin derivatives, urethane resin derivatives and polyester derivatives. Of these, polyvinyl alcohol derivatives and vinyl acetate derivatives are preferred, particularly with vinyl acetal monomer units.
JP 2002-293825, which corresponds to WO 02/059167, discloses a polyvinyl acetal characterized by containing one or more functional groups in one molecule e.g. a carboxyl group, a silyl moiety, a is halogen moiety, an amino group, a sulfhydryl group, a sulfonyl group, a thionyl group, an epoxy group, an oxazoline moiety, a maleimide moiety, a hydroxyl group etc. An ionic group such as an acidic group (e.g. a carboxyl group or a sulfonic group) or a basic group (e.g. containing a nitrogen atom) are preferred.
US 2002/0119406 discloses a photothermographic material comprising on a support a light-sensitive layer comprising an organic silver salt, light-sensitive silver halide grains, a reducing agent and a binder, wherein the photothermographic material exhibits not more than 30% of a rate of variation in fog density defined below: Rate of variation in fog density=[(DFog2−DFog1)/DFog1]×100(%) wherein DFog1 is a minimum density of the photothermographic material that has been subjected to development at a temperature of not less than 100° C. and DFog2 is a minimum density of the photothermographic material that has been subjected to the development and then further subjected to exposure to light at an illumination intensity of 300 lux and a temperature of 45° C. for 24 hrs. The binder preferably has a glass transition point of 70 to 105° C. and is preferably a polyvinyl acetal substantially having an acetoacetal structure or is a polymer compound represented by formula (V). Exemplary polymer compounds represented by formula (V) are disclosed with the composition given in Table 4 below:
TABLE 4vinylvinylalcoholacetateTgvinyl acetalvinyl butyral[mol %/[mol %/Polymer[° C.]{mol %/wt %][mol %/wt %]wt %]wt %]P-18351.59/57.422.11/30.6 24.6/10.61.7/1.4P-275 22.5/22.952.5/66.723.4/9.2 1.6/1.2P-48849.77/56.521.33/30.2 27.3/12.01.6/1.3P-59964.62/76.07.18/10.526.7/12.11.5/1.4P-69057.12/66.014.28/20.6 27.0/12.01.6/1.4P-77621.12/22.349.28/65.0 28.0/11.41.6/1.3P-87423.22/23.254.18/67.5 21.0/8.1 1.6/1.2
Pioloform™ BL16, a copolymer consisting of 42% by weight of vinyl acetal, 40% by weight of vinyl butyral, 16% by weight of vinyl alcohol and 2% by weight of vinyl acetate having a Tg of 84° C., produced by Wacker Chemie, is used as the sole binder in the thermosensitive element of a substantially light-insensitive thermographic material produced by AGFA-GEVAERT N.V. and marketed by AGFA-GEVAERT N.V. as AGFA FREEWAY™ film and by AUTOLOGIC as Autotype Aspect™ HR. The weight ratio of substantially light-insensitive organic silver salt to Pioloform™ BL16 in this thermosensitive element is approximately 1.0.